When naturally occurring subterranean pressure from gas, water and the like in an oil reservoir has fallen to a point that a well will not produce oil and gas at the earth's surface by way of such natural pressure, some method of artificial lift is necessary to continue producing liquid oil from that well.
A number of artificial lift techniques can be employed in such a situation, one of the most common being downhole pumps employed at the bottom of the well and operated by reciprocation of a string of sucker rods that extend from the downhole pump to the earths surface and a pumping unit situated thereat. The pumping unit reciprocates the sucker rod string and the downhole pump thereby actuating the pump. Each well is capped at the earth's surface with a wellhead to contain oil that is pumped to the earth's surface and to direct same through a conduit means (connected to the wellhead) to a collection site. The sucker rod string must necessarily extend out the top of the wellhead to reach the pumping unit. A seal is employed for preventing oil from passing out of the top of the wellhead where the sucker rod string exits. This seal means is conventionally called a stuffing box because of the stuffing, seal, or packing element therein that is employed to provide a seal around the sucker rod string to prevent oil leakage out of the stuffing box. In order to get a better seal at the stuffing box the portion of the sucker rod string that reciprocates through the stuffing box packing element(s) is specially coated and polished to give it a smooth surface. That particular section of the sucker rod string is called the polished rod.
The polished rod is lubricated with oil and or well fluids to reduce wear on the packing elements used as seal means inside the stuffing box. On the upstroke of the reciprocating polished rod a substantial length, e.g., 15 to 20 feet, of polished rod is pulled upward from inside the well through the stuffing box into the open atmosphere above the wellhead and stuffing box. Accordingly, during the full upstroke a long length and large surface area of oil coated sucker rod is exposed to the environment and often picks up wind borne particulates such as dust or even sand on its exposed oily surface. On the following full downstroke of the polished rod the particulates adhering to the surface thereof are carried into the stuffing box and through the seal (packing) elements thereby causing wear on those elements. Over time this makes the stuffing box more prone to leak well fluids into the environment where the polished rod exits the top of the stuffing box.
If for any reason the well is not pumped for a period of time the polished rod is not reciprocated through the stuffing box and the packing elements in the stuffing box can sometimes dry out so that when the pumping unit is again actuated well fluids can leak past the dried out packing and into the atmosphere surrounding the top of the wellhead.
If left leaking for a long enough period of time, a collection of oil on the ground near the base of the wellhead can accumulate. Also, during the upstroke of the polished rod well fluids may spray from the seal area of the stuffing box if the internal wellhead pressure is sufficiently high.
This invention provides an apparatus whereby normal pumping with the pumping unit and polished rod can be carried on, but the portion of the polished rod that exits the stuffing box on the upstroke is protected from the atmospheric elements outside the stuffing box. In addition, the stuffing box is contained in a manner such that any oil leakage therefrom even under pressure will be caught and contained at the wellhead in a manner such that such leakage does not reach the atmosphere or the ground and is caught in an easily disposable manner.